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  • 1. Enell, Carl-Fredrik
    et al.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Friedrich, Martin
    Singer, Werner
    Baumgarten, Gerd
    Kaifler, Bernd
    Hoppe, Ulf-Peter
    Gustavsson, Björn
    Brandström, Urban
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Kero, Antti
    Ulich, Thomas
    Turunen, Esa
    The Hotel Payload 2 campaign: Overview of NO, O and electron density measurements in the upper mesosphere and lower thermosphere2011In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 73, no 14-15, p. 2228-2236Article in journal (Refereed)
    Abstract [en]

    The ALOMAR eARI Hotel Payload 2 (HotPay 2) rocket campaign took place at Andoya Rocket Range, Norway, in January 2008. The rocket was launched on January 31, 2008 at 19:14 UT, when auroral activity appeared after a long geomagnetically quiet period. In this paper we present an overview of the HotPay 2 measurements of upper mesospheric and lower thermospheric (UMLT) electron, atomic oxygen (O) and nitric oxide (NO) densities. [O] and [NO] were retrieved from a set of three photometers, Night-Time Emissions from the Mesosphere and Ionosphere (NEMI). Faraday rotation receivers on the rocket and the EISCAT UHF incoherent scatter radar provided simultaneous electron density profiles, whereas the ALOMAR Na lidar and meteor radar measured the temperature profile and wind. The aurora was also observed with ground-based imagers. The retrieved oxygen number density profile has a maximum at 89 km, some 10 km lower than expected from earlier measurements and modelled profiles based on climatological averages (such as the MSIS model), and the retrieved NO densities are also lower than the expected. Satellite measurements indicate that subsidence over the winter pole controlled the densities. Quantitative chemistry model results based on climatological average atmospheric density and temperature profiles were, therefore, not in good agreement with the measured profiles. The Hotel Payload 2 measurements thus confirm the importance of downward transport from the thermosphere into the winter polar vortex.

  • 2. Guineva, V.
    et al.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Werner, R.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Neichev, S.
    Kirov, B.
    Bankov, L.
    Gramatikov, P.
    Tashev, V.
    Popov, M.
    Hauglund, K.
    Hansen, G.
    Ilstad, J.
    Wold, H.
    O-2 density and temperature profiles retrieving from direct solar Lyman-alpha radiation measurements2009In: Geomagnetism and Aeronomy, ISSN 0016-7932, E-ISSN 1555-645X, Vol. 49, no 8, p. 1292-1295Article in journal (Refereed)
    Abstract [en]

    The resonance transition P-2-S-2 of the atomic hydrogen (Lyman-alpha emission) is the strongest and most conspicuous feature in the solar EUV spectrum. The Lyman-alpha radiation transfer depends on the resonance scattering from the hydrogen atoms in the atmosphere and on the O-2 absorption. Since the Lyman-alpha extinction in the atmosphere is a measure for the column density of the oxygen molecules, the atmospheric O-2 density and temperature profiles can be calculated thereof. A detector of solar Lyman-alpha radiation was manufactured in the Stara Zagora Department of the Solar-Terrestrial Influences Laboratory (STIL). Its basic part is an ionization camera, filled in with NO. A 60 V power supply is applied to the chamber. The produced photoelectric current from the sensor is fed to a two-channel amplifier, providing analog signal. The characteristics of the Lyman-alpha detector were studied. It passed successfully all tests and the results showed that the so-designed instrument could be used in rocket experiments to measure the Lymanalpha flux. From the measurements of the detector, the Lyman-alpha vertical profile can be obtained. Programs are created to compute the O-2 density, atmospheric power and temperature profiles based on Lymanalpha data. The detector design appertained to ASLAF project (Attenuation of the Solar Lyman-Alpha Flux), a scientific cooperation between STIL-Bul.Acad.Sci., Stara Zagora Department and the Atmospheric Physics Group at the Department of Meteorology (MISU), Stockholm University, Sweden. The joint project was part of the rocket experiment HotPay I, in the ALOMAR eARI Project, EU's 6th Framework Programme, Andoya Rocket Range, Andenes, Norway. The project is partly financed by the Bulgarian Ministry of Science and Education.

  • 3.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology.
    Fan, Z. Y.
    Wademarsson, Tomas
    Stockholm University, Faculty of Science, Department of Meteorology.
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Llewellyn, E. J.
    She, C.-Y.
    Plane, J. M. C.
    Retrieval of the global mesopsheric sodium density from the Odin satellite2007In: Geophysical Research Letters, Vol. 34, no L04813Article in journal (Refereed)
    Abstract [en]

    Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid-latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.

  • 4.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Fan, Z. Y.
    Waldemarsson, T.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Llewellyn, E. J.
    She, C. -Y
    Plane, J. M. C.
    Retrieval of global mesospheric sodium densities from the Odin satellite2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 4, p. L04813-Article in journal (Refereed)
    Abstract [en]

    Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid- latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.

  • 5.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Christensen, Ole Martin
    Stockholm University, Faculty of Science, Department of Meteorology . Chalmers University of Technology, Sweden.
    Ivchenko, Nickolay
    Murtagh, Donal P.
    Chang, Seunghyuk
    Dillner, Joachim
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ekebrand, Terese
    Giono, Gabriel
    Hammar, Arvid
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Karlsson, Bodil
    Stockholm University, Faculty of Science, Department of Meteorology .
    Krus, Mikael
    Li, Anqi
    McCallion, Steven
    Olentšenko, Georgi
    Pak, Soojong
    Park, Woojin
    Rouse, Jordan
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    The MATS satellite mission - gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy2020In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 20, no 1, p. 431-455Article in journal (Refereed)
    Abstract [en]

    Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O-2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.

  • 6.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Optical studies of noctilucent clouds in the extreme ultraviolet2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 5, p. 1109-1119Article in journal (Refereed)
    Abstract [en]

    In order to better understand noctilucent clouds (NLC) and their sensitivity to the variable environment of the polar mesosphere, more needs to be learned about the actual cloud particle population. Optical measurements are today the only means of obtaining information about the size of mesospheric ice particles. In order to efficiently access particle sizes, scattering experiments need to be performed in the Mie scattering regime, thus requiring wavelengths of the order of the particle size. Previous studies of NLC have been performed at wavelengths down to 355 nm from the ground and down to about 200 nm from rockets and satellites. However, from these measurements it is not possible to access the smaller particles in the mesospheric ice population. This current lack of knowledge is a major limitation when studying important questions about the nucleation and growth processes governing NLC and related particle phenomena in the mesosphere. We show that NLC measurements in the extreme ultraviolet, in particular using solar Lyman-α radiation at 121.57 nm, are an efficient way to further promote our understanding of NLC particle size distributions. This applies both to global measurements from satellites and to detailed in situ studies from sounding rockets. Here, we present examples from recent rocket-borne studies that demonstrate how ambiguities in the size retrieval at longer wavelengths can be removed by invoking Lyman-α. We discuss basic requirements and instrument concepts for future rocket-borne NLC missions. In order for Lyman-α radiation to reach NLC altitudes, high solar elevation and, hence, daytime conditions are needed. Considering the effects of Lyman-α on NLC in general, we argue that the traditional focus of rocket-borne NLC missions on twilight conditions has limited our ability to study the full complexity of the summer mesopause environment.

  • 7.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Use of O2 airglow for calibrating direct atomic oxygen measurements from sounding rockets2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, Vol. 2, p. 801-812Article in journal (Refereed)
    Abstract [en]

    Accurate knowledge about the distribution of atomic oxygen is crucial for many studies of the mesosphere and lower thermosphere. Direct measurements of atomic oxygen by the resonance fluorescence technique at 130 nm have been made from many sounding rocket payloads in the past. This measurement technique yields atomic oxygen profiles with good sensitivity and altitude resolution. However, accuracy is a problem as calibration and aerodynamics make the quantitative analysis challenging. Most often, accuracies better than a factor 2 are not to be expected from direct atomic oxygen measurements. As an example, we present results from the NLTE (Non Local Thermodynamic Equilibrium) sounding rocket campaign at Esrange, Sweden, in 1998, with simultaneous O2 airglow and O resonance fluorescence measurements. O number densities are found to be consistent with the nightglow analysis, but only within the uncertainty limits of the resonance fluorescence technique. Based on these results, we here describe how better atomic oxygen number densities can be obtained by calibrating direct techniques with complementary airglow photometer measurements and detailed aerodynamic analysis. Night-time direct O measurements can be complemented by photometric detection of the O2 (b1g+X3g-) Atmospheric Band at 762 nm, while during daytime the O2 (a1ΔgX3g-) Infrared Atmospheric Band at 1.27 μm can be used. The combination of a photometer and a rather simple resonance fluorescence probe can provide atomic oxygen profiles with both good accuracy and good height resolution.

  • 8.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rapp, Markus
    Deutsches Zentrum für Luft und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany.
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Observations of NO in the upper mesosphere and lower thermosphere during ECOMA 20102012In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 30, p. 1611-1621Article in journal (Refereed)
    Abstract [en]

    In December 2010 the last campaign of the German-Norwegian sounding rocket project ECOMA (Existence and Charge state Of Meteoric smoke particles in the middle Atmosphere) was conducted from Andøya Rocket Range in northern Norway (69° N, 16° E) in connection with the Geminid meteor shower. The main instrument on board the rocket payloads was the ECOMA detector for studying meteoric smoke particles (MSPs) by active photoionization and subsequent detection of the produced charges (particles and photoelectrons). In addition to photoionizing MSPs, the energy of the emitted photons from the ECOMA flash-lamp is high enough to also photoionize nitric oxide (NO). Thus, around the peak of the NO layer, at and above the main MSP layer, photoelectrons produced by the photoionization of NO are expected to contribute to, or even dominate above the main MSP-layer, the total measured photoelectron current. Among the other instruments on board was a set of two photometers to study the O2(b1Σg+X3Σg-) Atmospheric band and NO2 continuum nightglow emissions. In the absence of auroral emissions, these two nightglow features can be used together to infer NO number densities. This will provide a way to quantify the contribution of NO photoelectrons to the photoelectron current measured by the ECOMA instrument and, above the MSP layer, a simultaneous measurement of NO with two different and independent techniques. This work is still on-going due to the uncertainties, especially in the effort to quantitatively infer NO densities from the ECOMA photoelectron current, and the lack of simultaneous measurements of temperature and density for the photometric study. In this paper we describe these two techniques to infer NO densities and discuss the uncertainties. The peak NO number density inferred from the two photometers on ascent was 3.9 × 108 cm−3 at an altitude of about 99 km, while the concentration inferred from the ECOMA photoelectron measurement at this altitude was a factor of 5 smaller.

  • 9.
    Lossow, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Dalin, P.
    Swedish Institute of Space Physics.
    Kirkwood, S.
    Swedish Institute of Space Physics.
    Schmidlin, F.J.
    NASA Goddard Space Flight Center, Wallops Island, VA.
    Fricke, K. H.
    Physikalisches Institut der Universität Bonn.
    Blum, U.
    Physikalisches Institut der Universität Bonn.
    Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign2009In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 9, p. 4407-4417Article in journal (Refereed)
    Abstract [en]

    The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E) with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios. From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1) a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

  • 10.
    Olofson, K. Frans G.
    et al.
    Göteborgs universitet, Kemiska institutionen.
    Svensson, Erik A.
    Göteborgs universitet, Kemiska institutionen.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pettersson, Jan B. C.
    Göteborgs universitet, Kemiska institutionen.
    Arctic aerosol and clouds studied by bistatic lidar technique2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, p. D18208-Article in journal (Refereed)
    Abstract [en]

    Aerosol and cloud studies were carried out with a polarimetric bistatic lidar setup at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) in Andenes (69°N, 16E°), Norway. The measurements were performed from 10 to 23 October 2006 and covered altitudes between 1.5 and 11 km, corresponding to scattering angles between 130 and 170°. The degree of linear polarization, PL, calculated from the experiments was compared with light scattering calculations using Lorenz‐Mie theory for spherical particles, the T‐matrix approach for nonspherical rotationally symmetric particles, and a geometric optics ray‐tracing method. Average PL values between 0.61 and 0.72 were obtained for the background aerosol under cloud‐free conditions. The aerosol results may be qualitatively reproduced by standard aerosol types if a suitable combination of coarse‐ and fine‐mode spherical particles is assumed. The PL values obtained for thin and mildly opaque clouds were in the range from 0.21 to 0.38. These results were not well described by spherical particles, and the results for relatively small prolate and oblate particles studied with the T‐matrix method tended to be slightly higher than the experimental values. Geometric optics calculations for hexagonal column ice particles with surface roughness were able to reproduce the experimental cloud data. This does not rule out contributions from other types of particles, and particle orientation effects may also have influenced the results. We conclude that the experimental results are consistent with earlier in situ studies of cirrus clouds, and the further development and application of the bistatic lidar technique is discussed.

  • 11. Olofson, K. Frans G.
    et al.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pettersson, Jan B. C.
    Bistatic lidar measurements of clouds in the Nordic Arctic region2008In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, no 26, p. 4777-4786Article in journal (Refereed)
    Abstract [en]

    Cloud studies were carried out with a polarimetric bistatic lidar setup at the Arctic Lidar Observatory for Middle Atmosphere Research in Andenes (69 degrees N, 16 degrees E), Norway. Measurements were performed at altitudes between 1.5 and 10.5 km, corresponding to scattering angles between 130 degrees and 170 degrees. The geometry, not restricted to the parallel or perpendicular laser polarization directions, gave a well-defined scattering angle, which together with polarization characterization, was used to investigate the scattering particles. The principles of the technique and the first results are presented together with an evaluation of the capabilities.

  • 12. Stevens, Michael H.
    et al.
    Gattinger, R. L.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Llewellyn, E. J.
    Degenstein, D. A.
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology.
    First UV satellite observations of mesospheric water vapor2008In: Journal of geophysical research. Atmospheres, Vol. 113, no D12, p. D12304-Article in journal (Refereed)
    Abstract [en]

    We report the first UV satellite observations of mesospheric water vapor. The measurements are of nonthermal OH prompt emission between 300–330 nm produced directly from the photodissociation of water vapor by H Lyman-α. This technique is most sensitive to water vapor concentrations between 70–90 km altitude. We present OH data from two limb scanning experiments: the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) and the Optical Spectrograph and Infra-Red Imager System (OSIRIS). Interpretation of the lower resolution (∼1 nm) OSIRIS spectra requires the rotational emission rate factors for OH(1,1) solar fluorescence between 313–318 nm, which we present for the first time herein. Comparison of water vapor concentration profiles with the most coincident profiles from the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite shows agreement to within 30% between 75–80 km for both MAHRSI and OSIRIS. We discuss the benefits of this promising new approach to measuring upper mesospheric water vapor and the need for new laboratory measurements to improve the analysis.

  • 13.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Size and shape of ice grains in the mesopause region2011In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 32, no 11, p. 3029-3041Article in journal (Refereed)
    Abstract [en]

    The paper is devoted to optical remote-sensing techniques successfully applied to investigations of the mesospheric aerosol layer, starting with a short history of the development of optical sounding experiments. In the following part, a theoretical basis of scattering measurements is discussed. A brief description of the theoretical principles of optical analysis of aerosol properties, ending with a survey of current activity and, as yet, unresolved problems is presented. It can be concluded that there is a consensus regarding the size range of mesospheric aerosol particles. The contribution of the smallest particles cannot be assessed by current optical methods. The combination of the scattering measurement with an electromechanical impact detector is a promising technique. The true size distribution, more correctly a statistical average of many possible distributions, must rely on numerical modelling. Regarding the shape of the particles, the noctilucent-cloud particles are not perfect spheres. New insight into this problem can be expected from the ongoing observational program of the Atmospheric Chemistry Experiment (ACE) and Aeronomy of Ice in the Mesosphere (AIM).

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